The present invention relates generally to the field of data communications over a network and, more specifically, to a method of performing Quality-of-Service (QoS) data communications over a short-cut path within a routed network.
Routing typically provides a hop-by-hop path (routed path) through an Internet Protocol (IP) network. A resource reservation protocol may then be utilized to reserve resources along each hop of the routed path. An example of a protocol for performing such resource reservation is the Resource ReSerVation Protocol (RSVP), which is a protocol for signaling QoS requests for IP flows. The handling of QoS requests is dependent on the link layer applied within a network. A connection-oriented link layer, such as for example Asynchronous Transfer Mode (ATM), typically provides extensive QoS mechanisms, and further has the capability to bypass the routed network by setting up end-to-end connections spanning multiple nodes.
Resource reservation (or allocation) protocols typically require that state information regarding flows be maintained at various nodes throughout the network. For example, RSVP requires that state information for each RSVP flow be maintained at each intermediate RSVP router along a path. This negatively impacts the scalability of RSVP in large routed networks, with a large number of QoS flows, for two primary reasons. Firstly, as state information must be maintained at each intermediate node of a path along which resources have been reserved, memory consumption by state information becomes prohibitive. For example, consider that with RSVP the state information that must be stored for each IP flow includes several IP addresses, source and destination ports, and 32-bit Logical Interface Handles (LIHs). This limits the scalability of RSVP in terms of the number of routers that can be allowed in a data path, and also in the number of simultaneous RSVP flows that a single node can support. Secondly, as each intermediate node is required to examine and process the contents of resource-reservation control messages, implementation of a resource-reservation protocol within a large network may prove to be processor intensive at the various nodes. For example, within the RSVP protocol, each RSVP PATH message needs be captured and processed at each RSVP node along the data path. Parsing and processing such RSVP messages imposes a heavy compute load on the network when this needs to be done at each RSVP node along a routed data path.
Multi-Protocol Over ATM (MPOA) and the Next Hop Resolution Protocol (NHRP) provide mechanisms for xe2x80x9cshortcuttingxe2x80x9d some of the hops along a routed path by setting by, for example, ATM Switched Virtual Circuits (SVCs) between ingress and egress points of the points of an ATM network, and diverting a data flow over the shortcut.
According to the present invention, there is provided a method of performing data communications over a network. A short-cut path is established through the network between an ingress node and an egress node. A data flow is propagated between the ingress and egress nodes over the short-cut path. A control flow, associated with the data flow, is encapsulated within a protocol not supporting quality-of-service. The encapsulated control flow is propagated from the ingress node to the egress node over a routed path through the network.
Responses to a control flow may be returned to the ingress node on the routed network.
Other features of the present invention will be apparent from the accompanying drawings and from the detailed description that follows.